Process for manufacturing writing-tablets of glass.



v No Drawing.

JAQKOB SCHAMBONY, or MiTNICI-I, GERMANY.

PROCESS FOR MANUFACTURING WRITING-TABLETS OF GLASS.

To all whom it may concern: I

Be it known that I, JAKOB SGHAMBONY,

citizen of Germany, residing at Munich,

Bavaria, Germany, have invented certain new and useful Improvements in Processes for Manufacturing Writing-Tablets of Glass; and I do hereby. declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

It is a part of the prior art to manufacture writing-tablets of glass by subjecting opaque or nearly opaque tablets or sheets of glass to a process of etching, which produces the necessary rough surface on the glass. Writing tablets of this kindhave several disadvantages and are therefore not suitable for use in schools. One disadvantage is that the grain produced by the etching is not of uniform, depth, which fact makes itself unpleasantly felt when writing, the pencil or style meeting with a varying resistance when movin over the surface. A further disadvantage is that writing or the like done with graphite or lead on these'tabthe tablet is rubbed with fine glass-paper lets is diflicult to remove, the tablets having a fatty feeling to the touch and being diflicult to clean. Thus in a short time the tablet becomes covered with a greasy film of graphite, which makes writing diflicult and also makes the drawing of a fine line impossible. The cleansing of these tablets is further impeded by the unequal graining, the deeper hollows becoming filled with graphite, which cannot be completely removed by the cleansing means. Wrltingtablets made of so-called biscuit-porcelain or the like possess similar disadvanta es.

The aim of the present invention is to provide a process for manufacturing writing-tablets'of glass, which do not possess these disadvantages and which are suitable for use in schools.

. According to the present invention the tablet of bone-glass or the like, after being etched and thus provided with a grain on its surface, is covered with a fine layer consisting of a metal-oxid mixed with glass flux which fills up the hollows of the graining and does not allow the graphite to adhere in greater quantities than necessary. The etching means may consist, for instance, principally of ammonium-fiuorid, hydrouoric acid and barium-sulfate. Hereupon Specification of Letters Patent.

Application filed August 11, 1910. Serial No. 576,700.

Patented Aug. 29, 1911.

whereupon the above-described covering is burned in, the glass-flux insuring the proper adhesion. In consequence of the treatment with glass-paper and also of the shrinking of the covering film or coating during burning, the raised portions of the glass grain will again-project thr'oughthe said covering film after the burning process.-

To describe my process more in detail, it is to be observed that under the same I etch the surface of a slab or plate of glass, such as bone-glass, with a solution of 120 parts of ammonium fluorid in 100 parts of water, to which are added 50 parts of hydrofluoric acid and 25 parts of barytes (barium sulfate). After this mixture has suificiently acted upon the surface of the glass, the same is-washed off and the glass is dried. Thereupon, the surface thus etched is coated with.

a fine layer suitable for burning, which consists in a mixture of a metal oxid or oxids, a flux and a small addition of a hinder, the metal oxids being so selected as to impart to the surface the desired color or tinge, such as greenish-white or yellowish-white. The covering film thus applied to the glass surface, thus coated, is then rubbed with fine-glass-paper after .being dried, whereupon the said fillm is'burned into the surface in any usual or desired manner. The tablet now possesses a uniform fine grain, over which the pencil moves easily and draws either a fine or thick line at will, and from which the writing or the like may be easily removed withthe aid of a wet sponge, cloth or with india-rubber. The convenience of cleaning the tablet is due on the one hand to the absence of deep hollows which would become filled with graphite and on the other hand to the fact that a part of the graphite lines are on the above-described film or layer.

The tablet lines either wet or dry before the covering layer is burned in. The lines may be drawn wet, for instance, with the help of a drawing pen and any color suited for burningv into glass;'when dry, theyare ground down with fine-glass-paper to such an extent as to be still visible, while not being palpably in relief. For drawing the lines dry, 2. coloring mass consisting of any suitable color for burning mixed with stearin may be used.

What I claim as my invention, and desire to secure by Letters Patent is:

1. The process for manufacturing writing glass surface.

2. The process for manufacturing writing surfaces which consists in etching the surface of the glass, then applying to the etched surface a layer of metal-oxid adapted to-be burned in, mixed with a glass-flux and, thereupon, burning the said layer into the glass surface.

3. The process for manufacturing writing surfacesfwhich consists in etching the writing surface of the glass plate, then applying to the etchedsurface a layer composed of a coloring .matter adapted to be burned in, mixed with a glass-flux,'then lightly grind ing the said layer and, finally, burning the 20 layer into the glass surface.

4:. The process for manufacturing Writing surfaces which consists in first etching a glass plate, then applying thereto a covering layer of coloring matter, adapted to be 25 burned in, combined with a glass-flux, then drawing lines onthe said surface with a J AKOB SCHAMBON Y.

Witnesses? A. V. W. Cormn, MATHILDE K. HELD. 

